StartExecution
Starts a state machine execution.
A qualified state machine ARN can either refer to a Distributed Map state defined within a state machine, a version ARN, or an alias ARN.
The following are some examples of qualified and unqualified state machine ARNs:
-
The following qualified state machine ARN refers to a Distributed Map state with a label
mapStateLabel
in a state machine namedmyStateMachine
.arn:partition:states:region:account-id:stateMachine:myStateMachine/mapStateLabel
Note
If you provide a qualified state machine ARN that refers to a Distributed Map state, the request fails with
ValidationException
. -
The following qualified state machine ARN refers to an alias named
PROD
.arn:<partition>:states:<region>:<account-id>:stateMachine:<myStateMachine:PROD>
Note
If you provide a qualified state machine ARN that refers to a version ARN or an alias ARN, the request starts execution for that version or alias.
-
The following unqualified state machine ARN refers to a state machine named
myStateMachine
.arn:<partition>:states:<region>:<account-id>:stateMachine:<myStateMachine>
If you start an execution with an unqualified state machine ARN, Step Functions uses the latest revision of the state machine for the execution.
To start executions of a state machine version, call
StartExecution
and provide the version ARN or the ARN of an alias that points to the version.
Note
StartExecution
is idempotent for STANDARD
workflows. For a
STANDARD
workflow, if you call StartExecution
with the same name
and input as a running execution, the call succeeds and return the same response as the
original request. If the execution is closed or if the input is different, it returns a
400 ExecutionAlreadyExists
error. You can reuse names after 90 days.
StartExecution
isn't idempotent for EXPRESS
workflows.
Request Syntax
{
"input": "string
",
"name": "string
",
"stateMachineArn": "string
",
"traceHeader": "string
"
}
Request Parameters
For information about the parameters that are common to all actions, see Common Parameters.
The request accepts the following data in JSON format.
- input
-
The string that contains the JSON input data for the execution, for example:
"input": "{\"first_name\" : \"test\"}"
Note
If you don't include any JSON input data, you still must include the two braces, for example:
"input": "{}"
Length constraints apply to the payload size, and are expressed as bytes in UTF-8 encoding.
Type: String
Length Constraints: Maximum length of 262144.
Required: No
- name
-
Optional name of the execution. This name must be unique for your Amazon account, Region, and state machine for 90 days. For more information, see Limits Related to State Machine Executions in the Amazon Step Functions Developer Guide.
If you don't provide a name for the execution, Step Functions automatically generates a universally unique identifier (UUID) as the execution name.
A name must not contain:
-
white space
-
brackets
< > { } [ ]
-
wildcard characters
? *
-
special characters
" # % \ ^ | ~ ` $ & , ; : /
-
control characters (
U+0000-001F
,U+007F-009F
)
To enable logging with CloudWatch Logs, the name should only contain 0-9, A-Z, a-z, - and _.
Type: String
Length Constraints: Minimum length of 1. Maximum length of 80.
Required: No
-
- stateMachineArn
-
The Amazon Resource Name (ARN) of the state machine to execute.
The
stateMachineArn
parameter accepts one of the following inputs:-
An unqualified state machine ARN – Refers to a state machine ARN that isn't qualified with a version or alias ARN. The following is an example of an unqualified state machine ARN.
arn:<partition>:states:<region>:<account-id>:stateMachine:<myStateMachine>
Step Functions doesn't associate state machine executions that you start with an unqualified ARN with a version. This is true even if that version uses the same revision that the execution used.
-
A state machine version ARN – Refers to a version ARN, which is a combination of state machine ARN and the version number separated by a colon (:). The following is an example of the ARN for version 10.
arn:<partition>:states:<region>:<account-id>:stateMachine:<myStateMachine>:10
Step Functions doesn't associate executions that you start with a version ARN with any aliases that point to that version.
-
A state machine alias ARN – Refers to an alias ARN, which is a combination of state machine ARN and the alias name separated by a colon (:). The following is an example of the ARN for an alias named
PROD
.arn:<partition>:states:<region>:<account-id>:stateMachine:<myStateMachine:PROD>
Step Functions associates executions that you start with an alias ARN with that alias and the state machine version used for that execution.
Type: String
Length Constraints: Minimum length of 1. Maximum length of 256.
Required: Yes
-
- traceHeader
-
Passes the Amazon X-Ray trace header. The trace header can also be passed in the request payload.
Type: String
Length Constraints: Minimum length of 0. Maximum length of 256.
Pattern:
\p{ASCII}*
Required: No
Response Syntax
{
"executionArn": "string",
"startDate": number
}
Response Elements
If the action is successful, the service sends back an HTTP 200 response.
The following data is returned in JSON format by the service.
- executionArn
-
The Amazon Resource Name (ARN) that identifies the execution.
Type: String
Length Constraints: Minimum length of 1. Maximum length of 256.
- startDate
-
The date the execution is started.
Type: Timestamp
Errors
For information about the errors that are common to all actions, see Common Errors.
- ExecutionAlreadyExists
-
The execution has the same
name
as another execution (but a differentinput
).Note
Executions with the same
name
andinput
are considered idempotent.HTTP Status Code: 400
- ExecutionLimitExceeded
-
The maximum number of running executions has been reached. Running executions must end or be stopped before a new execution can be started.
HTTP Status Code: 400
- InvalidArn
-
The provided Amazon Resource Name (ARN) is not valid.
HTTP Status Code: 400
- InvalidExecutionInput
-
The provided JSON input data is not valid.
HTTP Status Code: 400
- InvalidName
-
The provided name is not valid.
HTTP Status Code: 400
- KmsAccessDeniedException
-
Either your Amazon KMS key policy or API caller does not have the required permissions.
HTTP Status Code: 400
- KmsInvalidStateException
-
The Amazon KMS key is not in valid state, for example: Disabled or Deleted.
HTTP Status Code: 400
- KmsThrottlingException
-
Received when Amazon KMS returns
ThrottlingException
for a Amazon KMS call that Step Functions makes on behalf of the caller.HTTP Status Code: 400
- StateMachineDeleting
-
The specified state machine is being deleted.
HTTP Status Code: 400
- StateMachineDoesNotExist
-
The specified state machine does not exist.
HTTP Status Code: 400
- ValidationException
-
The input does not satisfy the constraints specified by an Amazon service.
HTTP Status Code: 400
See Also
For more information about using this API in one of the language-specific Amazon SDKs, see the following: